This invention shows how a TMI (Translation Mode Identifier) is used to selectively and quickly purge a TLB (Translation Lookaside Buffer), and how this technique is used to restore previously dispatched task's TLB entries via TMI matching. This lessens the number of overall TLB purges and improves performance. When a task is running, TLB entries associated with the task's TMI are used and created. When a task is no longer running the TLB entries associated with that task are not used. When the task is dispatched again, the TMI is restored and the TLB entries associated with this task are once again used. This unique task to TMI association allows less purging of the TLB.
In addition, we would note that there are publications and patents of which we are aware that are listed below, with a brief discussion of each of the publications and patents.
From U.S. Pat. No. 4,821,171 it may be appreciated that others have developed a code (which we will describe as a TMI-Translation Mode Identifier) associated with TLB entries. The code is for each switch to a new program, and the code has been assigned to each address translation created within the execution of the program. The code is updated to speed purging of translation buffers. This earlier patent does not illustrate how a code (our TMI) can be used in a multitasking environment to improve overall system performance while minimizing its cost to hardware as we will elaborate upon this in our detailed description.
Also, there are other patents dealing with TLB entries. U.S. Pat. No. 4,733,350 illustrates a method for purging a TLB by storing the affected addresses (those that need to be purged) in a purge register and provides for comparing these addresses to physical addresses from a TLB. However, this patent needs to store and subsequently compare physical addresses to identify those TLB entries that need to be purged.
U.S. Pat. No. 4,731,739 and U.S. Pat. No. 4,779,188 provide for fields in the TLB to store information, etc., but while these patents do have some relationship with a TLB, they have no particular relationship with our improvements.